'The clarity is so good, you feel like you are at the movies," says Jack, a plumber from Florida. "I think it's probably the greatest bit of technology to come along in the past 40 years or so," says Mike, a 23-year-old student from Massachusetts. "It's that good." Most new technologies have their fans, but some have more than others — in north America, high definition television (HDTV) has been hailed as an entertainment revolution.

High definition broadcasts are wowing viewers with their crystal-clear images, perfect in an age of widescreen home cinema viewing. The concept behind high definition is simple: fitting more information on screens. The European standard, known as PAL, transmits only 576 viewable lines (out of 625 lines) to a TV screen, regardless of its size. The European standard for HDTV, on the other hand, delivers either 720 or 1080 lines — a marked improvement.

HDTV, driven by coverage of sports such as American football, baseball and basketball, has firmly embedded itself in the US television market. Viewers enjoy the improved picture quality, and it is popular both inside the home and out of it. There are an estimated 6,000 sports bars around America showing HDTV, and nearly half of the country's consumers are planning to buy a high definition set for their home.

In Britain, where the broadcasting industry's emphasis has been on digital TV, there are no high definition services. But that is about to change. Some time next summer — perhaps for the World Cup in Germany — Sky will usher in a new era of British broadcasting by deliv­ering the first HDTV transmissions for the UK.

The company claims its service will put four times more data on to a screen than traditional transmissions, yielding "greater depth and tone of colours and textures, delivering a home-viewing experience similar to that offered in cinemas".

Using sport to drive a new premium platform is a familiar model for the Rupert Murdoch empire. Sky came to dominate the British satellite television market in Britain thanks to a judicious, and expensive, decision to make Premiership football the jewel in its crown. Analysts believe HDTV will follow the same path.

"This will be a top-tier service for those who want it," says Dermot Nolan, a director of the TBS consultancy. "They certainly won't stop showing Premiership football to ordinary viewers — there are just too many subscriptions. But Sky is not a charitable foundation — it is doing this because it can make a profit. If they get a million subscribers to pay £5 a month for high definition services, that's £60m a year on the bottom line."

And with figures like that, Sky is not the only broadcaster showing an interest. The BBC is already filming some shows in high definition — such as last month's drama-documentary Supervolcano — even if it does not yet broadcast the format.

Despite the radical effect HDTV is having in America, however, British broadcasters and hardware manufacturers must overcome a series of hurdles before Britons can tune in to it. Some industry figures worry that, in the short term at least, high definition may have a very limited impact on UK viewers.

There are a number of reasons why these fears may be well-founded. While there seems to be a real commitment to delivering HDTV in the UK, some aren't convinced the new transmissions will make any difference to what viewers actually see on their screens.

American analogue TV does not use the 625-line standard we are familiar with in Europe, employing instead the lower grade 525-line NTSC standard. This means the change from analogue to high definition is more keenly felt by US consumers. British customers — used to a better quality of picture and already switching to digital signals in droves — will only feel the benefit on large screens. Convincing them to make the change may be harder.

Most British broadcasters are also expected to debut the 720-line services rather than the 1080-line version. Such a move could short-change viewers, says Patrick Jocelyn, a director of Discreet, which makes systems for TV post-production facilities.

"If 720 is offered, I think some consumers won't see the immediate benefits over standard definition. They may think twice if the cost is much greater for the television set, receiver and service technology.

"For the broadcaster, it will be much more expensive to distribute 1080 rather than 720, so the final decision may well come down to the cost of transmission."

Tuning into the new signals will also involve consumers upgrading their hardware — not only their Sky boxes, but probably their TV set, too. To receive the transmissions, viewers require a set that is capable of displaying superior quality images, and can connect using a High Definition Multimedia Interface (HDMI). They also need to use software that can handle High-bandwidth Digital Content Protection (HDCP) — the system Sky will use to maintain copyright control of its transmissions.

While most large, flat screen sets launched this year by major electron­ics brands such as Sony and Philips are high definition-compatible, many of the LCD and plasma sets already sold won't work with HDTV transmissions. Some estimates put the figure as high as 90%.

As for the millions of viewers in the UK without a satellite dish, they may have a very long wait before they see any kind of HDTV transmission. In theory, broadcasters such as the BBC could offer HDTV over the same digital terrestrial system that delivers Freeview, but there are problems with the extra bandwidth required.

"I don't expect to be seeing high-definition broadcasts on terrestrial TV for some time due to the current lack of bandwidth," argues Dale Heathcote, of LCD screen manufacturer Humax. "That's an issue that won't be resolved until the government switches off the analogue TV transmissions."

Although some pilot areas have already had their analogue TV signals turned off, it is not likely to happen on a national scale for another decade. This prevents analogue being re-allocated for new services, stymieing the possibility of free-to-air high-definition services. And even if terrestrial services could be employed, there are doubts about whether it would be too expensive.

"It's not clear that a free-to-air HDTV service can work," agrees Nolan. "It certainly hasn't worked in America. The first generation of high definition was developed back in 1993, but it has had a lot of problems and lags a long way behind European digital terrestrial television. It is only cable and satellite HDTV that has been a success because they can charge for premium content."

But satellite and terrestrial transmissions aren't the only vehicle open for broadcasters. Cable providers NTL and Telewest are both hoping to offer HDTV transmission services next year. Delivering HDTV across the internet is also relatively cheap and easy to operate.

To view such transmissions, however, users will need a dedicated set-top box or a Windows Media Center PC, as well as an ultra-fast broadband connection. Despite an uptake in high-speed internet, most broadband in Britain simply isn't quick enough.

"HDTV over broadband requires at least 7Mbps per stream," says Roy Kirsopp, the sales director of Amino Communications. "Until the UK broadband infrastructure — which uses a standard DSL system that in practice has a maximum bandwidth of 4Mbps — is brought into line with other parts of the world, HDTV via broadband will not be a reality."

And the standards that people expect from their TVs and computers are different, says Geoff Zeider of Spirent, a company that manufactures test equipment for broadband systems. "IPTV [Internet Protocol television] is a new technology, and while PC users might not complain about buffering in some video streaming on a small screen, if it happens while they are watching HDTV they will be very disappointed."

Ultimately, though, TV set manufacturers remain confident that the Sky launch will lead to consumers swapping their old sets for HD-compatible flat screens. "It won't be too long before the momentum of HD will make it the next big thing in the home entertainment market," says Alan Joannidi, Sharp UK's senior LCD TV product manager.

There are a lot of hardware manufacturers who hope he is right. But even if it takes off, HDTV could prove to be more like the leap from analogue to digital TV, which only offered a slight improvement in picture quality, rather than the fundamental difference between VHS tape and DVD.

Sky, however, has a track record in using premium content to drive people towards new platforms. While only an avid TV fan will be tempted to shell out for both premium services and new hardware, if Sky can find enough interested consumers, it could push them towards otherwise unattractive HD services, despite all the barriers to entry.

"Wags often say that HDTV stands for 'high deficit TV' or 'high demographic TV'," says Nolan. "And to an extent, that's true. But there's no doubt it will be a very successful and profitable niche for Sky."